Fix handling of inherited check constraints in ALTER COLUMN TYPE.

tglsfdc · tglsfdc · commit 8e344eacdccc · 2012-11-05T13:36:31.000-05:00
This case got broken in 8.4 by the addition of an error check that
complains if ALTER TABLE ONLY is used on a table that has children.
We do use ONLY for this situation, but it's okay because the necessary
recursion occurs at a higher level.  So we need to have a separate
flag to suppress recursion without making the error check.

Reported and patched by Pavan Deolasee, with some editorial adjustments by
me.  Back-patch to 8.4, since this is a regression of functionality that
worked in earlier branches.
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
@@ -297,11 +297,11 @@ static void ATExecAddIndex(AlteredTableInfo *tab, Relation rel,
 			   IndexStmt *stmt, bool is_rebuild);
 static void ATExecAddConstraint(List **wqueue,
 					AlteredTableInfo *tab, Relation rel,
-					Constraint *newConstraint, bool recurse);
+					Constraint *newConstraint, bool recurse, bool is_readd);
 static void ATAddCheckConstraint(List **wqueue,
 					 AlteredTableInfo *tab, Relation rel,
 					 Constraint *constr,
-					 bool recurse, bool recursing);
+					 bool recurse, bool recursing, bool is_readd);
 static void ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 						  Constraint *fkconstraint);
 static void ATExecDropConstraint(Relation rel, const char *constrName,
@@ -2663,11 +2663,15 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 			break;
 		case AT_AddConstraint:	/* ADD CONSTRAINT */
 			ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
-								false);
+								false, false);
 			break;
 		case AT_AddConstraintRecurse:	/* ADD CONSTRAINT with recursion */
 			ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
-								true);
+								true, false);
+			break;
+		case AT_ReAddConstraint:	/* Re-add pre-existing check constraint */
+			ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
+								false, true);
 			break;
 		case AT_DropConstraint:	/* DROP CONSTRAINT */
 			ATExecDropConstraint(rel, cmd->name, cmd->behavior,
@@ -4516,7 +4520,7 @@ ATExecAddIndex(AlteredTableInfo *tab, Relation rel,
  */
 static void
 ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
-					Constraint *newConstraint, bool recurse)
+					Constraint *newConstraint, bool recurse, bool is_readd)
 {
 	Assert(IsA(newConstraint, Constraint));
 
@@ -4529,7 +4533,7 @@ ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	{
 		case CONSTR_CHECK:
 			ATAddCheckConstraint(wqueue, tab, rel,
-								 newConstraint, recurse, false);
+								 newConstraint, recurse, false, is_readd);
 			break;
 
 		case CONSTR_FOREIGN:
@@ -4581,10 +4585,18 @@ ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * AddRelationNewConstraints would normally assign different names to the
  * child constraints.  To fix that, we must capture the name assigned at
  * the parent table and pass that down.
+ *
+ * When re-adding a previously existing constraint (during ALTER COLUMN TYPE),
+ * we don't need to recurse here, because recursion will be carried out at a
+ * higher level; the constraint name issue doesn't apply because the names
+ * have already been assigned and are just being re-used.  We need a separate
+ * "is_readd" flag for that; just setting recurse=false would result in an
+ * error if there are child tables.
  */
 static void
 ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
-					 Constraint *constr, bool recurse, bool recursing)
+					 Constraint *constr, bool recurse, bool recursing,
+					 bool is_readd)
 {
 	List	   *newcons;
 	ListCell   *lcon;
@@ -4643,6 +4655,13 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	if (newcons == NIL)
 		return;
 
+	/*
+	 * Also, in a re-add operation, we don't need to recurse (that will be
+	 * handled at higher levels).
+	 */
+	if (is_readd)
+		return;
+
 	/*
 	 * Propagate to children as appropriate.  Unlike most other ALTER
 	 * routines, we have to do this one level of recursion at a time; we can't
@@ -4675,7 +4694,7 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 
 		/* Recurse to child */
 		ATAddCheckConstraint(wqueue, childtab, childrel,
-							 constr, recurse, true);
+							 constr, recurse, true, is_readd);
 
 		heap_close(childrel, NoLock);
 	}
@@ -6330,6 +6349,10 @@ ATPostAlterTypeParse(char *cmd, List **wqueue)
 	/*
 	 * Attach each generated command to the proper place in the work queue.
 	 * Note this could result in creation of entirely new work-queue entries.
+	 *
+	 * Also note that we have to tweak the command subtypes, because it turns
+	 * out that re-creation of indexes and constraints has to act a bit
+	 * differently from initial creation.
 	 */
 	foreach(list_item, querytree_list)
 	{
@@ -6373,6 +6396,7 @@ ATPostAlterTypeParse(char *cmd, List **wqueue)
 									lappend(tab->subcmds[AT_PASS_OLD_INDEX], cmd);
 								break;
 							case AT_AddConstraint:
+								cmd->subtype = AT_ReAddConstraint;
 								tab->subcmds[AT_PASS_OLD_CONSTR] =
 									lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);
 								break;
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
@@ -1150,7 +1150,9 @@ typedef enum AlterTableType
 	AT_EnableReplicaRule,		/* ENABLE REPLICA RULE name */
 	AT_DisableRule,				/* DISABLE RULE name */
 	AT_AddInherit,				/* INHERIT parent */
-	AT_DropInherit				/* NO INHERIT parent */
+	AT_DropInherit,				/* NO INHERIT parent */
+	/* this will be in a more natural position in 9.3: */
+	AT_ReAddConstraint			/* internal to commands/tablecmds.c */
 } AlterTableType;
 
 typedef struct AlterTableCmd	/* one subcommand of an ALTER TABLE */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
@@ -1476,6 +1476,28 @@ select * from another;
 (3 rows)
 
 drop table another;
+-- ALTER TYPE with a check constraint and a child table (bug before Nov 2012)
+CREATE TABLE test_inh_check (a float check (a > 10.2));
+CREATE TABLE test_inh_check_child() INHERITS(test_inh_check);
+ALTER TABLE test_inh_check ALTER COLUMN a TYPE numeric;
+\d test_inh_check
+Table "public.test_inh_check"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ a      | numeric | 
+Check constraints:
+    "test_inh_check_a_check" CHECK (a::double precision > 10.2::double precision)
+Number of child tables: 1 (Use \d+ to list them.)
+
+\d test_inh_check_child
+Table "public.test_inh_check_child"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ a      | numeric | 
+Check constraints:
+    "test_inh_check_a_check" CHECK (a::double precision > 10.2::double precision)
+Inherits: test_inh_check
+
 -- disallow recursive containment of row types
 create temp table recur1 (f1 int);
 alter table recur1 add column f2 recur1; -- fails
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
@@ -1092,6 +1092,13 @@ select * from another;
 
 drop table another;
 
+-- ALTER TYPE with a check constraint and a child table (bug before Nov 2012)
+CREATE TABLE test_inh_check (a float check (a > 10.2));
+CREATE TABLE test_inh_check_child() INHERITS(test_inh_check);
+ALTER TABLE test_inh_check ALTER COLUMN a TYPE numeric;
+\d test_inh_check
+\d test_inh_check_child
+
 -- disallow recursive containment of row types
 create temp table recur1 (f1 int);
 alter table recur1 add column f2 recur1; -- fails
